Family doctor



COLD SORES - a patient's guide


Cold sores are a common problem and this article provides suggestions on how to help limit outbreaks.


  • Cold sores are caused by a form of herpes virus (type 1)
  • They form small blisters on the lips, mainly at the edge of the mouth
  • They are extremely common, most people are infected during childhood
  • Cold sores are spread from direct contact or sharing drinks, dishes, and razors
  • They can recur because of stress, fever, colds, menstruation or sun exposure
  • The early use of an anti-viral cream may prevent a blister
  • Avoid contact with an infected person during an outbreak
  • Oral sex can spread the cold sores to the genitals

What is it?

Cold sores are also known as herpes labialis and fever blisters, and are caused by herpes type 1. This is a similar virus to herpes type 2, which is the usual cause of genital herpes.

Cold sores (type 1) can cause genital lesions as well through contact during oral sex and a percentage (20%) of new genital infections may in fact be due to type 1.

They form small blisters on the skin of the lips, mouth, and skin around the mouth. They commonly occur at the edge of the mouth.

They are extremely common and most people will have been in contact with the virus by the age of 20.

In young children they cause a condition called herpes stomatitis and involve the mouth - it may be painful and difficult to keep up fluid intake.

Cold sores are infectious and can be spread through direct contact, or touching infected razors, towels, dishes, utensils, and toothbrushes.

What are the symptoms?

There will be a tingling sensation at the site, followed by an itchy and burning feeling, and then the appearance of a blister. They usually appear around the lips, but other common sites include the nasal entrance.

The cold sore can appear between one or two weeks after contact with the virus, but the incubation period can be up to 20 days.

The blister will last about one week before starting to heal.

A cold sore can recur at the same sight, triggered by a number of factors including menstruation, stress, fever, drinking alcohol, or sun and wind exposure.

A skin infection (impetigo) may look similar to a cold sore.

Swabs can be done to confirm the virus, but usually the appearance is typical and the diagnosis made on this basis.

What can be done to help?

Avoiding sunburn (use sunblock) is helpful if recurrent blisters are a problem.

Applying an anti-viral cream such as Zovirax at the tingling stage can help prevent a cold sore from developing further.

The use of cold sore cream may also help to speed healing of the cold sore.

Simple pain relief e.g. paracetamol can be helpful.

Oral antiviral medications (e.g. Zovirax tablets) are not advised routinely for cold sores, but there are occasional exceptions to this.

How can they be prevented?

They can be prevented by avoiding contact with a person who has a cold sore. Do not kiss a child if you have a cold sore.

It is possible to spread cold sores to the genitals through oral sex. Oral sex and kissing should be avoided during an outbreak.

Avoiding excessive exposure to wind and sun may also prevent an outbreak. Use sunscreen around the lips while outdoors.

Getting help

Most people treat known cold sores themselves - however if there is doubt about the diagnosis, if they are very frequent or severe, medical advice should be sought.

See also:

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